1. Field of the Invention
The present invention relates to an encoding control circuit for controlling the number of generated codes in an image encoding circuit, and to an encoding circuit using the encoding control circuit.
2. Description of the Prior Art
Electronic devices very commonly employ a processing which converts analog image signals into digital signals by sampling the image signals and quantizing the sampling values. Moreover, the encoding processing such as compression processing for orthogonally transforming the sampling values is also performed. For example, the Hadamard transform corresponds to the above encoding processing.
Control of the number of generated codes is realized by applying division to each orthogonally-transformed component. The component of n-degree orthogonal transformation is shown as H=S(n) (n is 0 to n−1).
Encoding control is realized by diving a component H by a value Q (quantization step). For example, when H is a value shown by 10 bits, H can be shown by 7 bits when dividing H by Q=8 and it is possible to decrease the number of generated codes by a value equivalent to 7 bits.
However, when increasing the value of Q in this encoding control, it is impossible to restore an image to an original image after reverse orthogonal transformation because the quantization step becomes large and the quantity of information is reduced as a result of encoding. For example, in the case of MPEG encoding, the image quality may be greatly deteriorated due to block noise.